The present invention relates to the fabrication of devices. More particularly, the invention relates to patterning of a device layer on a substrate.
In device fabrication, one or more device layers are formed on a substrate. The layers are sequentially deposited and patterned to create features on the surface of the substrate. The layers can be patterned individually and/or as a combination of layers to form the desired features. The features serve as components that perform the desired functions, creating the device.
One type of device which is of particular interest is a light emitting diode (LED). Typically, an LED cell or pixel comprises one or more functional layers sandwiched between two electrodes to form a functional stack. Charge carriers are injected from both electrodes. These charge carriers recombine in the functional layer or layers, causing visible radiation to emit. Recently, significant advances have been made utilizing organic functional layers to form organic LEDs (OLEDs). Such devices are fabricated on rigid glass substrates having a thickness of about 0.3-1.1 mm.
Typically, OLED devices comprises a plurality of OLED pixels arranged to form a display, such as a flat panel display (FPD). A pixelated OLED device includes, for example, a plurality of first electrode strips formed on the substrate. The strips are arranged in a first direction. One of more organic layers are formed on the first electrodes strips. A plurality of second electrode strips is formed over the organic layers in a second direction. Typically, the first and second electrode strips are orthogonal to each other. The intersections of the first and second electrode strips form LED pixels.
The first electrode strips are created on the substrate by patterning an electrode layer. Conventionally, the electrode layer is patterned by photolithographic and etch processes. For example, a photosensitive resist layer is deposited on the electrode. The resist layer is exposed with radiation having the desired pattern defined by a mask. After development, unwanted resist is removed to expose portions of the electrode beneath. The exposed portions are removed by a wet etch, leaving the desired pattern on the electrode layer. Thus, conventional techniques for patterning the electrode require numerous steps, increasing raw process time and manufacturing cost.
As evidenced by the above discussion, it is desirable to provide a simplified process of patterning a device layer.
The invention relates to patterning a device layer on a substrate during device fabrication. In accordance with the invention, the patterning of the device layer an is achieved using a stamp with a pattern thereon. The pattern is formed by protrusions having a height greater than the thickness of the device layer to pattern the device layer. The stamp is pressed against the surface of the substrate under a load which patterns the device layer. The load is selected to precisely control cracking the edges of the patterned areas but without cracking the non-patterned areas.